1. Field of the Invention
The present invention relates to a method for manufacturing a silicon carbide semiconductor device, more particularly, a method for manufacturing a silicon carbide semiconductor device including a silicon carbide layer having an inclined side surface.
2. Description of the Background Art
Conventionally, it has been proposed to use silicon carbide (SiC) as a material for a semiconductor device. For example, it is proposed to use silicon carbide to form a trench gate type MOSFET (Metal Oxide Semiconductor Field Effect Transistor) (see Japanese Patent Laying-Open No. 2008-235546).
In this publication, it is proposed to form tapering side walls of a gate trench in order to improve breakdown voltage of a gate insulating film. Specifically, a semiconductor layer made of silicon carbide is partially removed by anisotropic etching using an etching mask having an opening pattern, and then is subjected to isotropic etching, whereby the gate trench formed in the semiconductor layer is provided with the tapering side walls.
When the side walls (side surfaces) of the gate trench are formed by means of isotropic etching as disclosed in this publication, it is difficult for each of the side surfaces to have a plane orientation sufficiently close to a specific crystal plane. If the side surface can be adapted to have a plane orientation close to such a specific crystal plane, various advantages can be obtained. For example, when a crystal plane allowing for high electron mobility is selected, a MOSFET having a low on-resistance can be obtained by increasing channel mobility.